While chairs to provide for sitting in a "knee rest" position are quite old, the idea of a chair for conversion from conventional to a knee rest chair is more recent.
The closest art known to applicant is set forth below.
U.S. Pat. No. 4,736,982 to Hwang teaches a chair which is convertible by changing the relative position of a seat and back rest cushions. A combining of conversion and adjustment of seat and back rest position is not disclosed nor is a fine and independent adjustment of same.
U.S. Pat. No. 4,765,684 to Kvalheim and Pedersen teaches a chair which is convertible by use of a novel operating and interlocking mechanism for the seat. This also lacks the adjusting features mentioned above.
None of the prior art discloses independent and fine relative adjustment of the seat and back rest while converting from conventional to knee rest position.